So I was doing some thought experiments with the Ability Oracle checks Mearls presents and it made me realize that, with three different tiers (as presented), there is really no need to calculate DCs for anything in the game anymore.
Let's say each of the three tables Mearls created is labeled "Difficult," "Dangerous," and "Doomed." Because these tables have been created with the full range of possibility modifiers across different metrics (no proficiency, proficiency, expertise) the Difficult/Dangerous/Doomed tables work at every level of the game 1-20.
Because of this, we can now take monsters and hazards and other DCs and say that the check is one of the three tiers, depending on a range of factors. For example, an enemy caster that is CR 5 cast Fireball on a 3rd level party. This is a Dangerous check, and you use that table to see who succeeds. Complications could be taking half damage, setbacks could be igniting due to the fireball.
You have a lever here where, perhaps, in addition to Advantage and Disadvantage you can modify the "danger class" of the check. If the party was 7th level against the same enemy, it is now a Difficult Check instead of a Dangerous one, meaning it is easier for them to pass. Or, the party is in a room filled with flippable tables, and this terrain turns this specific Dangerous check into a Difficult one (because you're flipping tables to eat the fireball).
Taken to the absolute extreme, you could even use this for AC. You could change the exact number required for a Success without complications to match a creature's AC, and that's for the baseline Dangerous check. Using the terrain to get an advantageous attack off could turn this into a Difficult check, which lowers the AC required to get a success against the monster. Likewise, the monster could have some buff that, until deactivated, it is actually a Doomed check to hit it, and its AC is buffed by +10.
These are just ideas right now that could lead to sweeping game changes or potentially work with the game as is. However, I think the richness in this idea is that it boils down all the calculations for math to three simple tables that could, in theory, be used to run the entire game off of. It may be too simplified for some but, to me, it feels so elegant because it produces so much information with every roll.
Tagging
@mearls to see this line of thinking too.
